The main objective of this work is ultimately to understand the genetic and molecular basis of chemotactic behavior in the bacterium Escherichia coli. Toward this end, we are attempting to construct a detailed genetic picture of the chemotaxis machinery of E. coli so that we can begin to ask meaningful biochemical questions about this system. Last year, the isolation and preliminary analysis of chemotaxis mutants were described and a working model of information processing was derived. Our current goal was to complete the behavioral analysis of these mutants and to test specific predictions of our model. We also hoped to identify additional components of the system in the course of these experiments.